Thin-film broadband and wide-angle devices for generating and sampling polarization states

ABSTRACT

Exemplary thin-film optical devices have first and second layer groups disposed as a layer stack on a substrate. The first layer group comprises a first PPN layer, a first LCP layer, and a first barrier layer all superposed. The second layer group is superposed relative to the first layer group, and includes a second PPN layer, a second LCP layer, and a second barrier layer all superposed. The first and second layer groups cooperate to polarize multiple wavelengths of an incident light flux in a broadband and/or wide-angle manner Each of the layer groups has an alignment layer, a respective liquid-crystal polymer layer, and a barrier layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/953,272, filed Nov. 27, 2015, which is a continuation ofInternational Application No. PCT/US2014/039778, filed May 28, 2014,which is a continuation-in-part of U.S. patent application Ser. No.13/287,910, filed on Nov. 2, 2011, which claims the benefit of U.S.Provisional Patent Application No. 61/456,184, filed Nov. 2, 2010, andU.S. Provisional Patent Application No. 61/516,621, filed Apr. 5, 2011.International Application No. PCT/US2014/039778 also claims the benefitof U.S. Provisional Patent Application No. 61/828,064, filed May 28,2013. All of these applications are incorporated herein by reference intheir respective entireties.

ACKNOWLEDGMENT OF GOVERNMENT SUPPORT

This invention was made with government support under Grant No.FA9550-09-1-0669 awarded by USAF/AFOSR and Grant No. FA8651-13-M-0085awarded by Air Force Material Command (AFMCLO/JAZ). The government hascertain rights in the invention.

FIELD

The disclosure pertains to thin-film optical devices such as polarizers,polarimeters, and polarized light emitters.

BACKGROUND

Polarization is one of the primary attributes of an optical field.Techniques for generating polarized light and measuring polarizationstates of light have been studied for decades. Conventional technologiesusually work only at single respective wavelengths of light. Forexample, in a conventional full-Stokes division of a focal-planepolarimeter, a retarder layer and a linear polarizer layer are utilizedin combination with a focal plane array. Different combinations ofretarder and polarizer orientations transmit different respectivepolarization states to respective underlying imaging pixels. (Forexample, a macro-pixel usually comprises a 0°, a 45°, a right-handcircular, and a 90° polarizer.) However, retardance conferred by asingle retarder layer is a function of wavelength. Therefore, apolarimeter comprising a conventional focal-plane array can samplepolarization states only at single specific wavelengths within a limitedband. These polarimeters have applications in a limited wavelength rangeand can require long exposure times because most of the light signalsoutside the wavelength range are filtered out.

U.S. patent application Ser. No. 13/287,910, (the “'910 application”)referenced above, discloses, inter alia, polarizers and methods forproducing them. The polarizers comprise photopolymers having molecularorientations established by exposure to linear polarized radiation(e.g., linearly polarized UV light). For example, on a substrate surfacea first alignment layer defines at least one respective alignmentdirection, wherein the first alignment layer comprises a respectivephoto-orientable polymer network (PPN). A first liquid crystal polymer(LCP) layer is situated on or proximate the first alignment layer sothat the LCP (including at least one guest material) is aligned with thePPN. A first barrier layer is disposed on the first LCP layer to protectthe underlying layers. These first layers comprise a first polarizationlayer group configured as, for example, a polarizer. A second alignmentlayer is proximate the first barrier layer, wherein the second alignmentlayer comprises a respective PPN defining a respective alignmentdirection. A second LCP layer is proximate the second alignment layer sothat second LCP (with respective guest material) is aligned with thealignment direction(s) of the second alignment layer. A second barrierlayer is disposed on the second LCP layer. The second layers comprise asecond polarization layer group configured as, for example, a retarder.A polarizer device having such a multilayer structure can extenduniformly (e.g., over the surface of the substrate) or can be formed asa “pattern,” i.e., in multiple discrete zones on the substrate.

Light-polarizing devices are also described in the '991 application, ofwhich an example comprises a substrate, a first polarization group oflayers on the substrate, and at least a second group of polarizinglayers. The groups of polarizing layers comprise respective alignmentlayers, LCP layers, and barrier layers, formed as summarized above.

Polarized-light emitters are also described in the '910 application, ofwhich an example comprises a substrate and a first group of polarizinglayers supported by the substrate. The first group comprises arespective alignment layer, a respective LCP layer, and a respectivebarrier layer. The LCP layer comprises a LCP material and one or moreanisotropic fluorophores that are aligned with the alignment layer. Asecond polarization layer group defining a retarder can be situatedrelative to the substrate. Application of fluorescence-excitationenergy, such as ultraviolet light or electrical current, causes thefluorophores to fluoresce. At least a portion of the fluorescent lightcan be transmitted through the LCP layer. At least a portion of thefluorescent light can be reflected back to the LCP layer in which thefluorescent light in a particular polarization state is absorbed by thealigned fluorophores.

Whereas the devices summarized above are useful for many applications,certain applications are unmet or poorly met by them. For example, thereare current needs for polarizer-based devices that are operable overwider ranges of light wavelength; i.e., so-called “broadband” ranges.Example broadband devices include, but are not limited to, polarizers,polarimeters, retarders and other waveplates; polarized-light emitters,displays, and cameras.

As used herein, “broadband” means an ability to operate at a widebandwidth that covers a useful range of the spectrum. For example, abroadband or achromatic wave plate can operate with flat retardance in awavelength range of 260-410 nm, 400-800 nm, 690-1200 nm, or 1100-2000nm. Other wavelength ranges are also possible. For such devices, thewavelength-dependence of the retardation is nearly flat (less than0.05-0.1 wave deviation) over the entire operating wavelength range. Incomparison, a narrow-band wave plate can operate in the range of, forexample, 550-650 nm (centered at 600 nm) with a wavelength dependence ofthe retardation being less than 0.1 wave deviation across the operatingwavelength range. It will be understood that operability in a broadbandmanner (e.g., in any of the broadband ranges noted above) generallyincludes operability in any of various narrower sub-ranges within thebreadth of the broadband range. For example, a broadband device operablein the range of 260-410 nm is also operable in the range of 270-280 nm,which is a sub-range of the broadband range.

There are also current needs for polarizer-based devices that areoperable over wider angles than currently available (or provided),particularly for improving displays. As used herein, “wide-angle” meansviewing angle greater than 160 degrees. An example of the viewing angleof a twisted nematic liquid-crystal display (LCD) ranges from 160-170degrees.

For many applications, such as light imaging, detecting, and display,there is a need for retarders, polarizers, and polarized-light emittersthat can operate at multiple wavelengths and angles. For example, itwould be useful if full-Stokes division-of-focal-plane (DoFP)polarimeters were available for operation at multiple wavelengths in theelectromagnetic spectrum (e.g., in the visible spectrum (400-700 nm))and at wider than conventional angles of incident light. In sensors,broadband operation would be useful for increasing the amount of lightreaching individual sensor elements or for producing larger signals.Because the angle of incidence of incoming light rays on a sensor isaffected by the locations of upstream optics, wider-angle operationwould accommodate a greater range of lens focal-lengths and lens-objectseparations than currently. In displays, patterned sets of broadbandretarders and polarizers would be useful for emitting light at multiplewavelengths at wide viewing angles in a patterned array such as an arrayof display pixels. This is because most displays need to operate in morethan one color and must be visible at more than one angle.

SUMMARY

Various embodiments described below are thin-film devices thatincorporate and exploit multilayer structures (i.e., comprising multiplepolarization layer groups: PPN/LCP/barrier layer) as disclosed in the'910 application into thin-film polarization devices to generate and/orsample light-polarization states over a broad band (wide wavelengthrange) and over wider angles than are currently available (or provided).These devices are in contrast with thin-film devices having only one ortwo polarization layer groups that collectively are optimized for andoperate at a single wavelength and/or angle. By adding at least a thirdpolarization layer group, thin-film devices are provided that operate atmultiple wavelengths and/or angles. For many applications, such asimaging and display, the thin-film devices comprise at least oneretarder layer group and at least one polarizer layer group. Forexample, in a division-of-focal-plane (DoFP) polarimeter, a set ofmultiple retarders and at least one polarizer can enable operation in adefined range of electromagnetic radiation (e.g., in the visiblespectrum (400-700 nm)) and at wide angles. Broadband operation allowsmore light or signals to reach a sensor. Since the angle of incidence ofincoming light rays on the sensor depends generally on the lens andobject locations, wide-angle operation accommodates a greater range oflens focal length and lens-object separation.

The retarders and polarizers can be “uniform,” by which is meant notpatterned. Patterned retarders and polarizers can be made by lithographyand etching of thin films (see U.S. Pat. No. 5,844,717).

The multilayer PPN/LCP/barrier structures of the devices describedherein are the result of simple fabrication techniques that providealternative fabrication techniques for producing broadband retarders andpolarizers exhibiting high spatial resolution with arbitrary retardanceand polarizations. The structures can be made flat ((i.e., lackingsignificant surface topography) to reduce light scattering and increaseextinction ratio. The presence of the barrier layer(s) protects theoptical layers from degradation and prolongs the operating lifetime ofthe device. Examples of a barrier layer, not intending to be limiting,are silicon dioxide, optical cement, parylene, and an index-matchingpolymer. The thickness of the barrier layer can range from 50 to 500 nm.In certain cases, the barrier layer can also serve as a polarizationlayer to reduce optical scattering and as an antireflection layer toimprove light transmission.

Broadband retarders can also be fabricated using twisted nematic liquidcrystal polymer. One or more layers of nematic liquid crystal can beused without twisted structures and with barrier layers located betweenthe structures. The structures are optimized for both broadband andhigh-angle operations.

A distinct advantage of the devices and methods set forth herein is thatthin-film devices capable only of narrow-band and/or narrow-angleoperation can be converted to wide-angle or wide-band simply by addingat least one additional polarization layer group. For example, anarrow-band device comprising a polarizing layer and one retarder can beconverted to a broadband device simply by adding a second retarder(comprising a respective alignment layer, at least one respective LCPlayer, and a respective barrier layer if required).

The various embodiments are not limited to sensing or emitting in onlythe visible spectrum; rather, the embodiments can also be applied toother wavelength ranges such as near-, short-, mid-, and far-infraredwavelengths.

As noted, at least two aspects are described herein. The first aspect isthe application of the broadband patternable micropolarizer based on amulti-layer structure of retarders and polarizer to construct apolarization detector, e.g., a polarization camera or imagingpolarimeter. The second aspect is the application of broadbandpatternable micropolarizers to create broadband light of a predeterminedpolarization state.

The foregoing aspects of the disclosed technology will become moreapparent from the following detailed description, which proceeds withreference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a representative embodiment of a liquidcrystal polymer (LCP)-based patterned device.

FIGS. 2A-2B are plan and sectional views, respectively, of arepresentative embodiment of a patterned photo-oriented polymer network(PPN)/LCP device in which the pattern elements are arranged in rows andcolumns.

FIG. 3 is a block diagram of a representative embodiment of a method forfabricating linear polarizable polymer (LPP)/LCP devices.

FIGS. 4A-4B are sectional and plan views, respectively, of a CCD imagesensor including a patterned LPP/LCP polarizer.

FIG. 5 illustrates a mask defining mixed chrome and LPP/LCP patternfeatures.

FIG. 6 illustrates an alternative mask defining mixed chrome and LPP/LCPpattern features.

FIG. 7 illustrates features of a light emitter based on a doped LCPlayer aligned with an LPP layer.

FIG. 8 is a schematic depiction of steps in a representative method forforming a device having a substrate, first and second alignment layers,first and second liquid crystal polymer (LCP) layers, and first andsecond barrier layers.

FIG. 9 is a schematic depiction of a region of a device having twogroups of polarization layers.

FIG. 10 is a schematic depiction of a region of a polarized lightemitter.

FIG. 11 is a schematic diagram of a focal-plane array (FPA) of aconventional full-Stokes division-of-focal-plane (DoFP) polarimeteroperable only as a narrow-band or narrow-angle device. Four pixels areshown in elevational view.

FIG. 12 is a schematic diagram of a FPA as used in a firstrepresentative embodiment of a DoFP polarimeter, comprising alinear-polarizer layer and two retarder layers. The retarder layers aremade of different materials and have different thicknesses. On the rightis an elevational view, and on the left are shown respectivepolarization directions at the first retarder layer group, at the secondretarder layer group, and at the uniform polarizer layer group.

FIG. 13 is a schematic diagram of a FPA as used in a secondrepresentative embodiment of a DoFP polarimeter, comprising alinear-polarizer layer and two retarder layers made of similar materialsbut having different thicknesses. On the right is an elevational view,and on the left are shown respective polarization directions at thefirst retarder layer group, at the second retarder layer group, and atthe uniform polarizer group.

FIG. 14 is a schematic diagram of a FPA as used in a representativeembodiment of a multipixelated polarized white light source, comprisinga linear-polarizer layer and two retarder layers of differentthicknesses but made of similar materials. On the right is anelevational view, and on the left are shown respective polarizationdirections at the first retarder layer, at the second retarder layer,and at the uniform polarizer.

FIG. 15 is a perspective “exploded” view of a broadband or wide-angleretarder comprising two polarization layer groups each including arespective LCP layer formed at a respective thickness, separated by abarrier layer. Fast (x, y) and slow (x′, y′) polarization axes areshown. The thickness of the LCP layers are not necessarily equal.

FIG. 16 is a schematic diagram of an array of four broadband ellipticalpolarizers (A, B, C, D) of a thin-film device comprising a linearpolarizer and two retarder layers made of different birefringentmaterials.

FIG. 17 is a schematic vertical depiction of an exemplary broadbandpolarizer comprising a liquid-crystal panel and two sets of broadbandpolarizers that operate at wide angles. The broadband polarizer operatesat wide angles and comprises a compensation retarder and a polarizer.The combination of two compensation retarders and the liquid-crystalpanel forms a tunable broadband and wide-angle retarder.

FIG. 18 is a schematic vertical depiction of an embodiment of abroadband wide-angle, 3-D organic LED (OLED) display comprising an OLEDpanel and a broadband polarizer. The broadband polarizer, which is alinear, circular, or elliptical polarizer, comprises a combination of abroadband wide-angle retarder and a linear polarizer.

DETAILED DESCRIPTION General Considerations

As used in this application and in the claims, the singular forms “a,”“an,” and “the” include the plural forms unless the context clearlydictates otherwise. Additionally, the term “includes” means “comprises.”Further, the term “coupled” does not exclude the presence ofintermediate elements between the coupled items.

The systems, apparatus, and methods described herein should not beconstrued as limiting in any way. Instead, the present disclosure isdirected toward all novel and non-obvious features and aspects of thevarious disclosed embodiments, alone and in various combinations andsub-combinations with one another. The disclosed systems, methods, andapparatus are not limited to any specific aspect or feature orcombinations thereof, nor do the disclosed systems, methods, andapparatus require that any one or more specific advantages be present orproblems be solved. Any theories of operation are to facilitateexplanation, but the disclosed systems, methods, and apparatus are notlimited to such theories of operation.

Although the operations of some of the disclosed methods are describedin a particular, sequential order for convenient presentation, it shouldbe understood that this manner of description encompasses rearrangement,unless a particular ordering is required by specific language set forthbelow. For example, operations described sequentially may in some casesbe rearranged or performed concurrently. Moreover, for the sake ofsimplicity, the attached figures may not show the various ways in whichthe disclosed systems, methods, and apparatus can be used in conjunctionwith other systems, methods, and apparatus. Additionally, thedescription sometimes uses terms like “produce” and “provide” todescribe the disclosed methods. These terms are high-level abstractionsof the actual operations that are performed. The actual operations thatcorrespond to these terms will vary depending on the particularimplementation and are readily discernible by one of ordinary skill inthe art.

Photo-Oriented Polymer Networks

Patterned and oriented arrangements of anisotropic molecules and/ormicrocrystals or nanocrystals on a substrate have many applications inoptical and electronic devices. One application is based onphoto-oriented polymer networks (PPNs), wherein a PPN can be used as analignment layer in a liquid crystal guest-host system. The PPN isaligned using polarized ultraviolet (UV) light. UV exposure need not beapplied over the entire PPN-coated substrate; rather, the exposureitself can be “patterned,” e.g., using microlithographic techniques, asdescribed in U.S. Pat. Nos. 5,389,698 and 6,496,239. After forming thealignment layer, a layer of a liquid crystal in a polymer (LCP) isformed superposedly on the aligned PPN layer to allow the LCP (and guestmaterial in the LCP) to align with the PPN. The LCP is often applied asa liquid solution of the LCP in a suitable solvent. An example guestmaterial comprises functionalized dichroic chromophores, present in aliquid solution of the LCP (referred to as a “host” material) in asuitable solvent. The chromophore(s) must align with the host system ina predetermined way. Another example guest material is a fluorophore: acompound made up of molecules that produce fluorescent light ifappropriately energized either by light or by electrical stimulation.The solubility and orientability of the guest-host system depend on thechemistry of the solvent, the liquid crystal material, and the guestchromophores.

In certain embodiments, chromophores, fluorophores, and/orsemiconductive polymers exhibit a liquid-crystal phase and can form apolymer film with addition of a photo-initiator and selected monomer.The liquid-crystal phase, consisting primarily of the chromophoresand/or semiconductive polymer, can act as both the “guest” and the“host.” The polymer film is typically applied as a liquid andsubsequently cured in a manner that achieves co-alignment of the guestand host (e.g., alignment with a PPN).

Various guest-host chemical systems described below provide goodsolubility and orientability of the guest in the host. Also describedare various devices that exploit this solubility and orientability.Whereas dichroic dyes (chromophores) can serve as guests, othertechnologically important classes of materials, such as carbon nanotubes(CNTs), n- and p-type semiconductor polymers, fluorophores, proteins,DNA, RNa, and/or other biological molecules can similarly be used. See,e.g., Zanchetta et al., PNAS 107:17497-17502 (2010), and Zanchetta etal., JAGS Communications 130:12864-12865 (2008), both of which areincorporated herein by reference.

A PPN and a guest-host system in polymer solution or uniform dispersioncan be deposited on a substrate in a pattern corresponding to apatterned array of CCD and/or CMOS image-sensor elements. The patternedarray can be formed by, for example, microlithography. In certainexamples, multiple layers of respective aligned guest-host systems canbe formed on a substrate to form structures that exploit the respectiveguest materials and their respective alignments. An example structure isa circular polarizer comprising a dichroic dye guest-host layer and aquarter-wave retarder.

LCPs are also referred to “reactive mesogens,” and an LCP layer caninclude a liquid-crystal material having one or more polymerizablegroups such as acrylate groups. For example, the acrylate groups can beassociated with acrylate monomers that can be polymerized into films,such as by UV radiation. The resulting cured LCP layer comprisespolymers having a “fixed” orientation. These and/or other LCP-layerformulations can be applied to rigid or deformable substrates, such as(but not limited to) glass, plastics, metal foils, or other surfaces.

PPNs are also referred to herein as linear photo-polymerizable polymers(LPPs). In some examples, fluorescent materials can be aligned in a LCPlayer in which the fluorescent materials are caused to emit light havinga selected state of polarization. These fluorescent materials arereferred to herein generically as “fluorophores.” An examplefluorophore, not intending to be limiting, is a fluorescent dye.

A PPN layer having one or more orientation directions established bysingle or multiple exposure to respective polarized radiation isreferred to herein as an “oriented” or “aligned” PPN layer. The alignedPPN layer is useful for aligning molecules in a LCP layer. Alignment ofa LCP layer with an oriented PPN layer can be accomplished even with oneor more intervening layers being situated between the PPN layer and LCPlayer; actual contact of the PPN and LCP layers with each other is notrequired.

As summarized above, polarized light for emission can be produced byinducing fluorophore guest material(s) to fluoresce. As used herein,polarized emission refers to emission of which a ratio of optical power(in at least one state of polarization) to total emitted power is atleast 0.5, 0.6, 0.7, 0.8, 0.9, or more. Optical devices can be producedfor use at visible optical wavelengths between about 400 nm and 700 nm,but devices for longer or shorter wavelengths can also be produced.

Formation of a device having multiple groups of layers is schematicallydepicted in FIG. 8. Applied to the surface of a substrate S is a firstalignment layer A₁ (which includes a corresponding PPN₁). Forming thefirst alignment layer A₁ includes aligning the PPNs of the layeraccording to a first orientation AL₁. A first liquid crystal polymerlayer L₁ (with guest G₁) is formed superposedly relative to the firstalignment layer A₁ so that the liquid crystal polymer molecules LCP₁(and guest material G₁) can be aligned according to the firstorientation AL₁. A first barrier layer B₁ is then formed. A secondalignment layer A₂ is formed (including the corresponding PPN₂) byapplying the PPN₂ and aligning them according to a second orientationAL₂. A second liquid crystal polymer layer L₂ (with guest G₂) is formedsuperposedly to the second alignment layer A₂, and the polymers arecaused to become coaligned according to the second pattern AL₂. A secondbarrier layer B₂ is then applied to, inter alia, protect the underlyinglayers.

Although FIG. 8 shows the layers A₁, A₂ as being continuous, it will beunderstood that these layers (and/or their respective liquid crystalpolymer layers L₁, L₂) can be formed according to respective patterns,e.g., to form a sensor array or to be arrayed according to a pattern ofan existing sensor array. It will also be understood that the depictedlayers can include one or more intervening layers.

FIG. 9 is a schematic view of a representative structure that can beformed by the method shown schematically in FIG. 8. Note that the layersA₁, L₁, B₁ comprise a first group of polarization layers, and the layersA₂, L₂, B₂ comprise a second group of polarization layers, both groupsbeing supported by a substrate S. In this structure, each group includesits own barrier layer.

Representative Embodiments of LCP-Based Patterned Devices

A first representative embodiment of a LCP-based patterned device isshown in FIG. 1. A substrate 102 having planar surfaces 102A, 102B iscoated with an LPP layer 104 applied to the surface 102A. The substrate102 can be glass, fused silica, silicon, germanium, or any othermaterial suitable for a particular application. Some applications, forexample, requiring high transmission of visible light are advantageouslyformed on optically transparent substrates. Alternatively, anelectrically conductive substrate, or a light-absorbing orlight-blocking substrate can be used. Although not shown in FIG. 1, thesubstrate 102 can include other coatings and/or surface treatments,wherein the LPP layer 104 is situated on a selected coating or surfacetreatment. For example, an electrically conductive coating, such as ametallic coating, can be applied to the surface 102A. In other examples,the coating can be both optically transparent and electricallyconductive, such as an indium tin oxide (ITO) coating.

The LPP layer 104 can be patterned by exposure to light that is linearlypolarized in one or more orientations. Such exposure can be achievedusing one or more pattern-exposure masks. The resulting LPP layer 104can have a spatially variable orientation suitable for achievingco-alignment of liquid crystal material (in a suitable polymer solution)in a subsequently applied LCP layer 106. The LCP layer 106 can include,in addition to the liquid crystal material which serves as a host, aguest such as a dichroic dye, a fluorescent dye or other fluorophore, anorganic semiconductor, carbon nanotubes, or other material that can beinduced to align with the liquid crystal material.

As shown in FIG. 1, the LPP layer 104 defines multiple regions 104A,104B having similar or respectively different alignments, according tothe intended function of the device. Different alignments can beachieved by selective exposure of the layer to respectively differentlinear polarizations of UV radiation. The LCP layer 106 hascorresponding alignment regions 106A, 106B. As an example, in FIG. 1,alignments in the regions 106A, 106B are mutually orthogonal; but, otheralignments are possible.

While many applications can be addressed using a single guest-host layergroup such as the alignment layer 104 and corresponding LCP layer 106,one or more additional guest-host layer groups can be provided, with orwithout respective alignment layers (a single alignment layer can beused to achieve alignment of multiple LCP layers in different respectivegroups). In the FIG. 1 embodiment, a second LPP layer (alignment layer)108 is situated on a first LCP layer 106, and a second LCP layer 110aligned in direction(s) established by the second LPP layer 108. Thus,two layer groups are formed, each comprising a respective LPP layer andrespective LCP layer. The LPP layers 104, 108 can be processeddifferently to achieve different orientations thereof, according todifferent patterns. Alternatively to the depicted configuration, thesecond LPP layer 108 can be omitted, wherein the second LCP layer 110aligns in response to alignment directions established by the first LPPlayer 104. The second LCP layer 110 can include the same or a differentguest material as the first LCP layer 106; alternatively, the second LCPlayer 110 can include no guest material at all. For example, the secondLCP layer 110 can be configured to serve as an optical retarder, and thefirst LCP layer 106 can be configured to provide a suitable retardancebased on layer thickness.

In other embodiments additional LCP layers (and LPP layers) can be addedto the configuration shown in FIG. 1. These additional layers caninclude one or more respective metallic or semiconductor materials, forexample. An important additional layer in many embodiments is a barrierlayer. Respective barrier layers (each comprising a respectiveprotective material) desirably are situated between layer groups. Forexample, a first barrier layer can be located between the first LCPlayer 106 and the second alignment layer 108, and a second barrier layercan be located on the second LCP layer 110. Respective barrier layerscan be used separate LCP layers of respective layer groups and/oralignment layers of respective layer groups.

A given device can include multiple substrates, such as a secondsubstrate 112. If desired, an alignment layer (e.g., a respectiveorientated LPP layer or a conventional rubbed polyimide layer) can beprovided at the surface of the second substrate 112. In theconfiguration shown in FIG. 1, the second LPP layer 108 provides auniform respective orientation, to which the second LCP layer 110 hascommon alignment. The second LCP layer 110 can include one or more guestmaterials, such as fluorophores, carbon nanotubes, or other materials.The LCP layers 106, 110 can include the same or respectively differentguest materials; alternatively, one or both LCP layers can have no guestmaterial at all. Typically, LPP and LCP layers exhibit birefringence,and optical retarders with spatially varying optical axes can be formedwithout using a guest material in a LCP layer.

A representative embodiment of a patterned single-layer-group device 200is shown in FIGS. 2A-2B. The device includes a substrate 202, an LPPalignment layer 204, and an LCP layer 206. The alignment layer 204 issegmented (patterned) into an exemplary five-by-five array of patternregions that define five LCP regions 206A-206E each of which can have adifferent alignment. More or fewer pattern regions can be provided (afive-by-five array is used here for convenient illustration). In variousexamples, all pattern regions in one or more selected rows or columnshave similar alignments, while adjacent rows or columns have differentalignments. Other examples are possible having other respectivearrangements of alignment directions. The LCP layer 206 in each regioncan include one or more guest materials such as one or morefluorophores, dichroic dyes, carbon nanotubes, organic semiconductors,or other guest materials, which can be similar or different in eachregion. The alignment layer 204 is divided into alignment regions204A-204E for alignment of the respective LCP regions 206A-206E.

Methods for Fabricating Devices Having at Least One Layer Group

A representative fabrication method is illustrated in FIG. 3. At 302, anLPP layer is applied to the surface of a substrate by spin-coating orother suitable process. The LPP layer is destined to become an alignmentlayer. If the substrate surface is not planar, it may be planarizedbefore forming the LPP layer. At 304, the LPP layer is exposed topatterned linearly polarized light, typically by situating a patternedchrome-on-quartz mask proximate the LPP layer, or by projecting UVlight, patterned by passage through a mask, onto the LPP layer to alignit. The mask can define transmissive apertures (e.g., regions lacking achrome coating) for the respective desired pattern. At least onetransmissive aperture can include a respective λ/2 retarder layer thatrotates the polarization of incident UV to provide the respective regionwith a desired selected respective alignment. Alternatively, a series ofexposures can be made of different selected apertures to provide thecorresponding regions of the LPP layer with desired respectivepolarization orientations. An LCP material is selected at 306, and oneor more suitable guest materials are identified at 308. Guest materialsgenerally have appreciable solubility, typically in range of 1 to 1050mg/mL in the desired LCP solution. The guest material desirably also isable to continue, after combining it with the LCP, to serve the functionfor which it was selected. Candidate guest materials having little to nosolubility in the LCP solution typically fail to be present insufficient concentration in the LCP layer for the intended type ofdevice. Some fluorescent guest materials exhibit substantially reducedquantum efficiency due to quenching or other phenomenon when the guestmaterial is included in an LCP layer. A selected guest material is addedto the LCP material at 310, and at 312 the resulting mixture is coatedonto the LPP layer by spin-coating or other technique. At 314, the LCPlayer is cured by exposure to UV radiation. Regions not completely curedcan be removed by solvent at 315. At 316, additional layers areselected, and layer selection and formation continues at 302. Additionallayers of LCP and/or LPP can be applied in the same manner as describedabove, with the same or different patterns and guest materials. If alldesired layers have been formed, at 318, LPP/LCP layer formation stops.At 320, a barrier layer is provided, typically using a UV-curableoptical adhesive, to cover and enclose the LPP (alignment) layers andLCP layers except at layer edges. Whereas a LPP layer usually canprovide alignments that are more reproducible and more readily patternedfor LC alignment than conventional rubbed alignment layers (e.g., rubbedpolyimide layers), the alignment layer(s) used in the method describedabove can be a rubbed layer, particularly if patterning of the alignmentlayer is not likely to be required.

Example 1: Micropolarizer on a Sensor Array

A micropolarizer array can be fabricated directly on an imaging sensor,such as a charge-coupled device (CCD), a complementarymetal-oxide-semiconductor (CMOS) sensor, or a display device, such as aliquid-crystal display (LCD), organic light-emitting diode (OLED)display, or plasma display. A representative device is illustrated inFIG. 4, in which a CCD 402 includes an array 404 of pixels 404 _(u),where I, J are integers that refer to row and column number,respectively, of respective pixels. For color-image sensors, the pixels404 _(u) can include two or more color elements; usually, each pixel 404_(u) includes a collection of four color elements. Of the four colorelements, at least a respective one is associated with each of red (R),green (B), or blue (B) colors established by respective color filters.Here, a “pixel” can refer to any of multiple sensor elements (e.g., red,green, and blue color elements in a Bayer color arrangement), any ofvarious regions of an image, or any of multiple sensor elements that arepart of an array of sensor elements. Image sensors and arrangements ofcolor filters for such sensors are described in U.S. Pat. Nos. 3,971,065and 6,783,900, and in Dillon et al., IEEE Trans. Electron. Devices 25:97(1978), all of which are incorporated herein by reference.

The image sensor 402 can have a planar or other exterior surface onwhich a passivation layer 412 or other protective coating, such as alight-transmissive insulator made of BPSG, PSG, silicon dioxide, siliconnitride, polyimide, or other suitable material. The PPN alignment layer414 is situated on the passivation layer 412, and is patterned byexposure to one or more polarized UV beams that has been patterned bypassing through one or more masks. This patterning defines thePPN-orientation directions of the layer, which can vary from pixel topixel (including from color element to color element in a color imagesensor). An LCP layer 416 (including a dichroic dye and/or other guestmaterial) is situated on the LPP layer 414. If desired, a barrier(protective) layer and a layer of microlens can be provided on the LCPlayer 416.

A device as shown in FIG. 4 can be fabricated on an existing imagesensor, wherein the various image pixels of the sensor are associatedwith respective pattern elements of the device to form retarders orpolarizers, for example, defined by the patterned LPP/LCP layers.Pattern elements can be aligned based on lithographic mask alignmentsperformed when forming the layers on the sensor. Polarization extinctionratios of at least 2:1, 5:1, 10:1, 20:1, 50:1, 100:1, or greater arepreferred in most applications.

Example 2. Polarized-Light Emitters

In this example an LPP-aligned LCP element or device is a polarizedlight emitter in which the guest material comprises one or more suitablefluorescent dyes. An exemplary fluorescent dye can be selected from thevarious benzothiadiazole-based fluorescent dyes (these are called “BTD”dyes). Alternatively, the perylene-based dyeN,N′-di(pentyl)perylene-3,4,9,10 tetracarboxylic diimide can be used.The perlyene-based dye is also an organic semiconductor as discussed inother examples below. Synthesis of these dyes is described in Koge etal., Chem. Phys. Lett. 354:173 (2002), incorporated herein by reference.

By incorporating a fluorescent dye as a guest material in the LCP layer,the fluorescent dye co-aligns with the liquid crystal in the LCP, basedon orientations produced by UV exposure of the LPP. Subsequent exposureof the aligned fluorophore/LCP guest-host mixture to a suitableelectromagnetic radiation (at a wavelength(s) suitable for excitingfluorescence from the fluorophores) produces a substantially polarizedfluorescence. Emission intensity can be increased by increasing dyeconcentration without reducing the extent of polarization of thefluorescence.

In fluorophores in which UV absorption is polarization-dependent aswell, an incident UV flux used to excite fluorescence is at leastpartially polarized after exiting the fluorophore guest-host layer. Thispolarized UV can be directed through an additional 214 retarder layer toa reflective layer. The flux from the fluorophore layer can then bereflected back to the fluorophore layer through the λ/4 retarder so asbe in a state of polarization that is effectively absorbed by thefluorophore to increase fluorescence intensity.

FIG. 10 schematically depicts a polarized emitter according to anexample configuration. The depicted emitter comprises a substrate Shaving a reflective surface M. On the substrate is a “stack” of thefollowing layers: a retarder R, an alignment layer A in which the PPNshave a selected orientation, a LCP layer L in which liquid crystalpolymers and guest material(s) (fluorophores) are aligned to thealignment layer A. Protecting these layers is a barrier layer B. Thedepicted structure is one in which production of fluorescent light bythe fluorophores is caused by incoming fluorescence-exciting radiationFE. In the liquid crystal polymer layer L, the radiation FE stimulatesproduction of fluorescent light F, which propagates through the retarderR and reflects from the surface M. In this configuration a portion ofthe incident fluorescence-exciting radiation FE can be transmitted bythe LCP layer L to the retarder R and reflective surface M that drivethe portion back to the LCP layer L so as to be in a state ofpolarization that is effectively absorbed by the co-alignedfluorophores.

Example 3: Micropolarizers Comprising Carbon Nanotubes (CNTs)

CNTs can be used as a guest material in an LCP, in which the CNTs arealigned with an LPP layer (alignment layer) as shown generally in thedevices discussed above. Example LCPs for use with CNTs are LCPs basedon poly (p-phenylene terephthalamide), a compound having alkyl groupsand a pyrene group. The CNTs can be single-walled CNTs (“SWCNTs”). ASWCNT/LPP mixture can be made by first dissolving the LCP incyclopentanone, followed by adding the CNTs. Sonication of the mixtureyields a uniform dispersion of the SWCNTs in the LCP. The dispersion canbe spin-coated on a suitable substrate (e.g., patterned glass), therebyproducing an aligned film of the SWCNTs. In the aligned film the CNTsexhibit polarization properties.

Example 4: Oriented Semiconductors

Any of various organic semiconductors can be utilized as guest materialsin LCP. An example n-type organic semiconductor is N,N′-di(pentyl)perylene-3,4,9,10 tetracarboxylic diimide (PTCDI), which produces apolarized emission of yellow light. PTCDI molecules have a strongtendency to aggregate, but when provided as a guest in an LCP, theresulting films of PTCDI/LCP exhibit optical properties similar to filmsin which the PTCDI is known to be in homogeneous mixture or solution,suggesting that there is actually almost no aggregation. The resultingpolarizers have applicability in, for example, polarized organic-LED(“OLED”) applications such as OLED displays.

Example 5: Fabrication of Devices Comprising Multiple Layer Groups

Devices can be made that comprise multiple groups of layers, whereineach group comprises at least a respective alignment layer and arespective LCP layer. These groups can provide multiple respectivecombinations of PPN and LCP, and the groups can be layered successivelyto generate different optical elements such as color filters andelliptical or circular polarizers. One or more groups can include oromit other materials that nevertheless could be added to the liquidcrystal polymer, such as dichroic dyes, fluorescent dyes, or CNTs. Anexample process for a circular retarder having three LCP layers includesthe following steps: (a) formation of a 0-degree aligned LPP layer(first alignment layer); (b) superposedly forming a first LCP layer onthe first alignment layer, the first LCP layer having a quarter-waveoptical thickness (some oriented LPP layers provide considerablebirefringence, and the LCP can be selected in consideration of theretardation provided by the LCP); (c) forming a second LPP layer (secondalignment layer) on the quarter-wave LCP layer (the second LPP in thisexample is aligned at 45 degrees relative to the first alignment layer);(d) coating the second alignment layer with a second LCP layer in whichthe LCP material is mixed with a dichroic “guest” material, therebyforming a 45-degree linear polarizer; (e) forming a third LPP layer(third alignment layer) on the second LCP layer, the third alignmentlayer being aligned at 90 degrees relative to the first alignment layer;and (f) forming on the third alignment layer a third LCP layer providingquarter-wave retardation. Desirably, the three layer groups areseparated from each other in this “stack” of layers by respectivebarrier layers.

This three-layer-group structure (quarter-wave retarder/linear polarizerat 45 degrees/quarter-wave retarder) forms a left-handed circularpolarizer, and can be referred to as a homogeneous circular polarizer.

Example 6. Additional Guest Materials

While some examples are described herein with reference to particularguest materials such as fluorophores, dyes, or n- and p-type organicsemiconductors, other guest materials can be utilized in certainapplications. Examples are depicted below in Formula 1A and Formula 1B:

In Formulas 1A and 1B, each Y independently may independently be anoxygen atom or a sulfur atom. In the NR⁴ groups, each R⁴ mayindependently be a hydrogen, an aliphatic, an aryl, a heteroaryl, or aheteroaliphatic. Each R¹ may independently be an aliphatic or aryl, moretypically an alkyl (cyclic or acyclic), alkenyl (cyclic or acyclic), oralkynyl, even more specifically a C₁-C₁₀ alkyl, a C₁-C₁₀ alkenyl, or aC₁-C₁₀ alkynyl. In preferred embodiments, Formula 1A encompassescompounds in which R¹ is a C₈ alkyl, and Formula 1B encompassescompounds in which R¹ is a C₄ alkyl. X may be a halogen (independently abromine, a chlorine, a fluorine, or an iodine), and p may range from 0to about 4. Particular disclosed embodiments have Formulas 1C and 1D,illustrated below.

In Formula 2, above, each Y independently may be selected from oxygen,sulfur, and NR⁴ wherein R⁴ may be selected from hydrogen, aliphatic,aryl, heteroaryl, and heteroaliphatic. R² may independently be an alkyl(cyclic or acyclic), an alkenyl (cyclic or acyclic), or an alkynyl. AnR² may be substituted, wherein 1 to 3 hydrogen atoms are replaced with agroup selected from alkyl (cyclic or acyclic), aryl, alkenyl (cyclic oracyclic), and alkynyl. R² may be selected from C₁-C₂₀ alkyl; C₁-C₂₀alkenyl; and C₁-C₂₀ alkynyl. More specifically, R² may independently bea C₅-C₁₇ alkyl, a C₅-C₁₇ alkenyl, or a C₅-C₁₇ alkynyl. Even morespecifically, R² may independently be a C₁₇ alkyl, a C₁₅ alkyl, a C₁₁alkyl, a C₇ alkyl, or a C₅ alkyl. According to Formula 3, n ranges from0 to about 10, more typically from 1 to about 5. Py may independently bea pyrene or pyrene substituted with one or more halogen atoms (selectedfrom chlorine, fluorine, bromine, or iodine), alkyl groups, alkenylgroups, alkynyl groups, and heteroalkyl groups. For example, Py is:

Other specific embodiments have Formula 4 or 5, illustrated below.

In Formula 5, Y may independently be an oxygen or a sulfur. In NR⁴, R⁴may independently be a hydrogen, an aliphatic, an aryl, a heteroaryl, ora heteroaliphatic. R² is as described earlier above. R³ mayindependently be a hydrogen, a halo, an aliphatic, an aryl, aheteroaryl, or a heteroaliphatic, wherein m ranges from 0 to about 2.

Other embodiments comprise compounds having Formula 6:

Example 7: Tuning Dye Quantum Efficiency by Varying Excitation byWavelength

Dye quantum efficiency (QE) is defined as the number of emitted photonsdivided by the number of absorbed photons. QE is a function of both theexcitation wavelength and the emission wavelength. In an example, a405-nm laser diode was used to provide the excitation wavelength. A filmof the dye was placed in an integrating sphere connected to a calibratedfiber spectrometer. A coated LCP/dye sample was then placed in thecenter of the integrating sphere and a power spectrum of the sample wasobtained. Based on the power spectrum, the QE of each dye was estimated.In general, QE depends on the peak absorption of the dye. A higher QEwas obtained from dye 7A than from either dye 7B or 7C because theexcitation wavelength of 405 nm is closest to the peak absorption of dye7A:

Example 8. Patterned Waveplates

A patterned waveplate was fabricated using an LPP material (“ROP-103”)and an LPC material (“ROF-5102”) supplied by Rolic Technologies(Switzerland). An exposure system was developed to align and cure theROP-102 and ROF-5102 layers, respectively. A Hamamatsu LC5 UV lightsource was collimated and filtered (passband of 280 nm to 350 nm) andthen linearly polarized using a dichroic UV polarizer. The sample havingthe LPP layer to be oriented was placed on a rotational stage forexposure with an arbitrary direction of UV polarization. The UV-beamintensity at the stage was 12 μW/cm². Exposure times varied based on thenumber of alignment directions and substrate reflectivity. The coatingand alignment process for ROP-103 was (1) spin coat at 2500 RPM for 60seconds, (2) bake for 5 minutes at 175° C. to evaporate residualsolvent, and (3) perform alignment exposure(s). The resulting filmthicknesses were approximately 50 nm and of negligible retardance.Patterned alignment was achieved by adding a contact mask during a firstexposure. The mask was then removed, followed by rotating the stage (andsubstrate) 90°, and performing a second exposure.

The LCP “ROF-5102” was applied at a thickness associated with operationas a half-wave plate at a selected wavelength. The thickness andretardance exhibited by ROF-5102 were functions of spin rate.Application of the LCP material to LPP-coated substrates was byspin-coating at 850 rpm for 2 minutes, followed by annealing at 52° C.in an oven for 3 minutes, followed by exposure to 50 mW broadband UVlight for five minutes in a nitrogen atmosphere to cure the material.For operation as a half-wave plate at 532 nm, the thickness of theROF-5102 film is about 2.2 μm, and retardance is controlled to within±5% across 1.5-inch diameter substrates.

The patterned waveplate can be used as, for example, a patternedretarder.

Example 9. Mixed Chrome and LC Features

Substrates can also include combinations of chrome and LC features. Withreference to FIG. 5, a mask 500 is formed on a substrate having apatterned chrome layer formed as chrome regions 508-511, a patterned LPPlayer (alignment layer), and an LCP layer defining pattern regions514-516 and 518-519 in a first pattern area 530 and a second patternarea 532, respectively. Other combinations of chrome and LPP/LCP patternfeatures can be used. With reference to FIG. 6, a mask 600 includes asubstrate having a patterned chrome layer defining alternative patternlines 608-611, a patterned LPP layer (alignment layer), and an LCP layerhaving alternatingly oriented pattern lines 614-616.

Example 10. Patterned LCP Polarizers

Patterned polarizers can be fabricated that comprise at least one groupof LPP/LCP layers. In this example, the LPP material was LIA-01 fromDainippon Ink and Chemical. The LCP material was “RMS03-001C” fromMerck, delivered as a 30% (w/w) solution of propylene glycol monomethylether acetate (PGMEA). As noted above, the LCP is a reactive mesogenthat cures under UV light. Various dichroic dyes were purchased fromHayashibara Biochemical Laboratories, Inc., and round substrates made ofsoda-lime glass were used. An optical adhesive (Norland Optical Adhesive60) was used as a barrier layer. UV exposures were made using aHamamatsu Deuterium Fiber Optic Lamp, adjusted to provide an intensityof 20 mW/cm² for making exposures.

In a typical example, a 1.5″-diameter soda-lime wafer was spin-coatedwith LPP at 2000 rpm and dried at 95° C. for two minutes. The selectedLPP material was rewritable. Hence, the entire substrate was firstexposed with LPUV for 30 seconds at 0° using the deuterium fiber-opticlamp. A dark-field Air Force Resolution chrome mask was then placed incontact with the substrate. Then, the substrate/mask assembly wasrotated 90° and a second exposure was performed for 180 seconds,resulting in formation of a second pattern orthogonal to the firstpattern. A mixture of LCP and a selected dichroic dye was spin-coated onthe patterned LPP substrate.

More uniform polarizing coatings can be produced using dichroic dyesthat are readily miscible in the liquid crystal. A 10 mg/ml stocksolution of a selected dichroic dye in CHCl₃ was prepared and mixed withan equal volume of LCP-RMS03-001C solution in PGMEA. The solution of dyeand LCP in a CHCl₃/PGMEA mixture was then spin-coated on the alignedpatterned substrate at 1000 rpm and dried for 2 minutes at 55° C. toremove residual solvent. As the solvent evaporated, the LC/dye mixturealigned to the LPP pattern in a nematic phase. The substrate was thenexposed to unpolarized UV light at 50 mW/cm² intensity for six minutesto cure the material, thereby producing a durable thin film.

For generating multilayer elements, such as circular polarizers, twosuccessive layer groups (each having a respective alignment layer andLCP layer) are spin-coated onto the substrate. The first layer groupforms a patterned retarder (obtained by spin-coating undoped LCP), andthe second layer forms a uniform linear polarizer (obtained byspin-coating the mixture of dye and LCP). An optical adhesive was usedas a barrier layer between the two LPP/LCP layer groups, applied byspin-coating at 2500 rpm and UV curing for 5 minutes at an intensity of50 mW/cm².

Representative dyes are listed in the table below, but alternative dyescan be used.

Dye Visible λ_(max) in λ_(max) 10 mg/mL No. Color CHCl₃ Polarizer G-207Yellow 387 nm 386 nm G-241 Purple 553 nm 599 nm G-472 Blue 619 nm 652 nmIn other examples, multiple dyes are mixed together produce a “gray”polarizer. For use, each dye was diluted with CHCl₃ to 2 μg/mL. The thusdiluted dyes were then mixed together in various ratios. Preferredmixtures suitable for a color-neutral polarizer were estimated andmeasured in a spectrometer. Optimal ratios were 10:10:2 Blue:yellow:blueor 5:5:1 (blue:yellow:red).

Polarized-Light Emitters

FIG. 7 illustrates features of an embodiment of a polarized-lightemitter based on an aligned LCP layer. In FIG. 7 a substrate 702 isprovided with a first conductive layer 706 such an opaque or transparentlayer of a metal or metal oxide (e.g., indium tin oxide, abbreviated“ITO”). A patterned or otherwise oriented LPP layer 704 (alignmentlayer) is situated on the conductive layer 706. A LCP layer 708 issituated on the alignment layer 704, and a second conductive layer 710is provided on the LCP layer 710. The LCP layer 708 includes a suitableguest material such as an organic semiconductor. Application of anelectrical voltage across the conductive layers 706, 710 injects chargecarriers (as well as their respective recombination products) into theintervening layers, resulting in emission of polarized light. Thepolarization state of the emission is based on the particular alignmentin the LCP layer 708.

The LCP/LPP layers can be patterned as desired to produce patternedemission. Patterning can be by, for example, microlithography, resultingin formation of a desired array of individual light emitters, whereineach emitter includes respective first and second electrodes that areindividually controlled to activate the pattern elements individually.For example, row and column conductors can be provided, based on theconductive layers (e.g., the layers 706, 710), to activate correspondinglight-emitter elements defined by individual intervening LCP and LPPlayers. In some examples, first and second LCP layers with n-type andp-type organic semiconductor guests, respectively, are configured toprovide p-n junctions, but single layers or other organic LEDconfigurations can alternatively be used.

Additional Devices and Applications

Optical sensors such as charge-coupled devices (CCD) and complementarymetal-oxide semiconductor (CMOS) devices can be provided with patternedor unpatterned polarizers and/or retarders as described above. Opticalfilters such as conventional thin-film or absorptive filters can includeone or more groups of LCP/LPP layers that serve as polarizers (e.g.,linear, circular, or elliptical polarizers), or retarders of arbitraryretardation such as quarter-wave or half-wave retardation. The LCP/LPPlayers can be patterned or unpatterned, and structures having more thanone layer group can include different patterns on some layer group(s)compared to other layer group(s). Representative applications in thisregard include three-dimensional displays, interferometry, opticalstorage, polarimeters, and polarization-sensitive cameras.

In some applications, a so-called “pixelated phase mask,” comprising apatterned polarizer or retarder based on one or more LPP/LCP layergroups can be configured for use in spatial phase multiplexing ininterferometry. For example, a patterned retarder made up of multiplelayer groups or of one layer group can comprise retarder patternelements of the same or varying retardation and with the same or commonalignment. A patterned polarizer can be provided having a regular orother predetermined arrangement of polarizer elements so that orthogonaltest and reference wavefronts incident to the patterned polarizerproduce an interference pattern this is detected by an array detector.Typically, the pitch of a patterned polarizer/retarder is the same as oran integer multiple of the pixel pitch of the detector array. Uses ofsuch pixelated phase masks are described in Brock et al., U.S. Pat. No.7,230,717, which is incorporated herein by reference. In some examples,a pixelated phase mask includes quarter-wave retarders and polarizingelements, or other combinations of polarizing elements and retarderelements, typically selected to produce interference between incidentorthogonally polarized test and reference wavefronts.

Broadband Devices, General

This disclosure also includes incorporating multi-layer structures asdescribed above (e.g., devices having multiple PPN/LCP layer groups)into devices providing broadband (wide wavelength range) and/orwide-angle performance for generating and sampling polarization statesand for use as polarized-light emitters. Devices currently known aregenerally capable of operation at a single wavelength and/or narrowangle of light. By employing multiple layer groups in a device asdescribed below, it is possible to optimize devices for operation atmultiple wavelengths and/or angles. Each such layer group (e.g.,retarder and polarizer) comprises at least a respective alignment layerand a respective LCP layer.

In various embodiments described below, multiple groups of respectivealignment layers and LCP layers are used to provide broadband retarders,polarizers, and light emitters exhibiting high spatial resolution whileproducing desired selected retardance(s) and polarization(s). Also,strategic use of barrier layers ensures that the various optical layers(alignment layers and corresponding LCP layers) are protected. Barrierlayers can also provide desirable planarity and lack of surfacetopography of the layers, which serve to reduce light scattering andprovide increased extinction ratios. Barrier layers also prolong theoperating lifetime of the devices and can serves as antireflectioncoatings.

In the LCP layers of some embodiments, twisted nematic LCPs are used.The LCP layers in other embodiments comprise nematic liquid crystalmolecules that lack twisted structures. In any event, the structures areuseful for specific broadband and/or large-angle applications.

Multi-Pixelated Broadband Imaging Polarimeters

A pixelated polarimeter produces multiple pixelated intensitymeasurements through different polarization filters. A division offocal-plane (DoFP) polarimeter utilizes a polarization focal-plane array(FPA) that is analogous to a Bayer color-filter FPA in that neighboringpixels on an image sensor have different respective filters. Usually theFPA pattern consists of an array of 0°, 45°, 90°, and 135° linearpolarizers; however, such a configuration is only capable of measuringthe linear components of polarization, i.e., not all the components ofthe Stokes vector. To obtain a complete polarization measurement,measurements of elliptical and circular polarization components are alsorequired.

A full-Stokes DoFP polarimeter having a configuration describedgenerally in the '910 application is shown schematically in FIG. 11, inwhich the FPA is shown in a side-elevational view. The depicted portionof the FPA constitutes a “macro-pixel,” comprising sixteen correspondingpixels in four groups 4, 6, 8, 10. I.e., each group 4, 6, 8, 10comprises four respective pixels 4 a, 6 a, 8 a, 10 a. The polarimeterincludes one λ/4 retarder layer 18 and one polarizer layer 12 disposedon a sensor 14 serving as a substrate. Although not detailed in thefigure, the polarizer layer 12 and the retarder layer 18 each comprise arespective alignment layer and a respective LCP layer. A “buffer layer”(barrier layer) is disposed on the polarizer layer 12. Although notshown, a second barrier layer can be disposed on the retarder layer 18.The barrier layer(s) protect the retarder layer and polarizer layer andcan also serve as a respective planarization layer.

Incident light 16 having a particular polarization profile passesthrough the retarder 18 and polarizer 14 to the sensor 14. Note that thepolarization profile of the incident light 16 is the same for all pixels4, 6, 8, 10, but the polarization states of respective light reachingcorresponding pixels of the sensor 14 are different for each pixel.I.e., the sensor 14 receives respective polarized light from thepolarizer 12 such that each group 4, 6, 8, 10 of sensor pixels receiveslight of a respective polarization state, as determined by the retarder18 and polarizer 12 (shown are 0°, 45°, RCP, and 90°). Whereas eachorientation combination of retarder and polarizer transmits a differentpolarization state to the respective pixel below, retardance produced bythe single retarder 18 is a strong function of the wavelength of thelight 16 passing through it. Hence, a polarimeter configured as the DoFPshown in FIG. 11 can only sample polarization states of incident lightat a single specific wavelength within a narrow wavelength band and atsmall angles. This conventional polarimeter has a limited number ofapplications and usually requires long exposure times when used forimaging or sensing of incoming light.

Various embodiments described hereinbelow overcome the narrow-wavelengthcharacteristic of the device shown in FIG. 11. Certain embodiments areDoFP polarimeters configured to obtain data on polarization states ofincoming light at multiple wavelengths. To such end, the embodimentscomprise multiple (at least two) retarder layers that collectivelyproduce retardance over a defined range of wavelengths of incominglight, and thus are called “broadband” devices. The specific range ofwavelengths depends upon material, thickness, and polarizing function ofthe retarder layers. The polarizing layer and each retarder layercomprises a respective alignment layer and a respective LCP layeraligned with the alignment layer. The materials of the alignment layersneed not be the same, and the materials of the LCP layers need not bethe same (but, they can be). By way of example, one or more retarderlayers can comprise a respective combination of two different materialsto minimize variation of the retardation with wavelength.

FIG. 12 is a schematic diagram of a first embodiment of a polarimeterthat comprises a linear polarizer 22, a first retarder 24, and a secondretarder 26. These components are formed as respective layers on asupportive substrate 32 (glass plate in this embodiment). The polarizer22 and retarders 24, 26 each comprise a respective alignment layer and arespective LCP layer (not detailed). A respective isolation layer(barrier layer) 30 a separates the polarizer 22 from the second retarder26, and a respective barrier layer 30 b separates the second retarder 26from the first retarder 24. The retarders 24, 26 can have differentrespective thicknesses and can comprise different types of birefringentmaterials. (But, the thicknesses and/or materials can be the same.) Fourpixels A, B, C, D are shown. In each pixel the respective fast-axisangles of the two retarders 24, 26 are perpendicular to each other(e.g., compare the pixel A of the first retarder with the pixel A of thesecond retarder). Thus, the pixels A, B, C, D perform as respectiveelliptical polarizers.

By way of example, with appropriate selection of material and thicknessof each retarder 24, 26, the resultant retardance of each pixel A, B, C,D can be about 135°, within a 5% variation over a defined range ofwavelengths of incoming light 28, by compensating the chromaticbehavior. The resultant fast-axis angles of the pixels A, B, C, D in thesecond retarder 26 are, in this example, +15.1°, −15.1°, +51.7°, and−51.7°, respectively, relative to the vertical direction. (Compare withthe fast-axis angles in the first retarder 24.) These four pixels A, B,C, D perform as respective broadband elliptical polarizers, and areoptimized for inclusion in a polarimeter exhibiting a highsignal-to-noise ratio. Note that respective isolation layers (barrierlayers) 30 a, 30 b are situated between the layers 24, 26 and betweenthe layers 22, 26. The substrate 32 in this embodiment serves as alight-incidence surface.

FIG. 13 is a schematic diagram of the FPA of a second embodiment of aDoFP polarizer. This embodiment comprises a linear polarizer 42 and tworetarders 44, 46. The polarizer 42 and retarders 44, 46 each compriserespective alignment layers and LCP layers (not detailed) aligned withthem. The retarders 44, 46 in this embodiment have different thicknessbut are made of the same material. The fast-axis angles of the tworetarders are not perpendicular to each other since birefringencecompensation does not work directly when using similar materials. By wayof example, the resultant fast-axis angles of pixels A, B, C, D are+15.1°, −15.1°, +51.7°, and −51.7°, respectively, relative to thevertical direction.

In a specific example, the fast-axis angles of the retarders 44, 46rotate within ±30° oppositely. For example, if rotation is ±10°, thefast-axis angles of the pixels A, B, C, D of the first retarder 44 canbe +25.1°, −5.1°, +61.7°, and −41.7°, respectively, (see left-hand panelof FIG. 13), while the fast-axis angles of these pixels of the secondretarder 46 can be +5.1°, −25.1°, +41.7°, and −61.7°, respectively, asshown in FIG. 13. With appropriate selection of material thickness, theretardances produced by the pixels A, B, C, D can be 135°, with a 10%variation over a defined range of wavelengths. The pixels A, B, C, D canfunction as broadband elliptical polarizers of a polarizer exhibiting ahigh signal-to-noise ratio.

Note that the embodiments of FIGS. 12 and 13 can be pixelated or uniform(not patterned). For example, in a device such as shown in FIG. 13, thefirst retarder 44 is uniform, the second retarder 46 is pixelated, andthe polarizer 42 is uniform. A pixelated configuration is typicallyaccording to a particular pattern, which can be achieved bymicrolithography, for example.

Multipixelated Broadband Polarized Light Sources

A broadband micropolarizer based, as described above, on multiple layergroups (each comprising a respective alignment layer and a respectiveLCP layer) can be configured as a patterned source of broadband light(e.g., white light) of a predetermined polarization state(s). The lightsource can be configured to produce a pixelated multi-polarizedbroadband light, with particular applications in displays. In manyembodiments the light source can be patterned as an array ofnon-polarized light sources, with corresponding arrays of optics asrequired (including at least one polarization filter).

FIG. 14 is a schematic diagram of an exemplary embodiment for producingmulti-polarized broadband light. Light emitted from a pixelatedlight-intensity modulator 62 passes sequentially through a uniformvertical polarizer 64, a first retarder 66, and a second retarder 68.Similar to the second embodiment, the retarders 66, 68 each comprise arespective alignment layer and a respective LCP layer aligned with thealignment layer. In this embodiment the materials of the retarders 66,68 are the same, but the retarders have different thickness. Therespective polarization properties of the retarders 66, 68 can beestablished by controlling the materials, the thickness, the dimensions,and other respective properties of the individual retarders. In thisexample, the corresponding fast-axis angles of the two retarders 66, 68are rotatable within ±30° oppositely. The respective fast-axis angles ofthe pixels A, B, C, D of the first retarder 66 can be +25.1°, −5.1°,+61.7°, and −41.7°, respectively, while the respective fast-axis anglesof the second retarder 68 can be +5.1°, −25.1°, +41.7°, and −61.7°,respectively, relative to the vertical direction. The macro-pixels ofthe output light have four different elliptical polarization states.Continuing with the example above, the major-axis angles of the pixelsA, B, C, D are +15.1°, −15.1°, +51.7°, and −51.7°, respectively,relative to the vertical direction. The ellipticities and orientationsvary less than 10% from each other over a defined range of wavelengths.The depicted macro-pixel devices can function as pixelatedmulti-polarized sources of broadband light. Note also the respectiveisolation layers 50 a, 50 b between the first retarder layer 66 and thepolarizer layer 64 and between the first and second retarder layers 66,68.

Polarizer Categories

Categories of polarizers of various embodiments described herein are setforth in the following:

Mechanism Birefrin- Polarization Absorption Interference Reflectancegence linear dichroic crystal thin-film wire grid birefringent dichroicdye stacks Brewster's crystal type circular opt.-active cholesterichelical wire opt.-active molecules liq. crystal structure crystalAccording to the above, patterned circular polarizers, based on opticalinterference, can be fabricated using cholesteric LCPs. Patternedinfrared (IR) polarizers, which operate by absorption, can be fabricatedusing IR dichroic dye as guest materials in LCP hosts. Also, real-timefull-Stokes polarization imaging can be achieved using an array ofdifferent micropolarizers.

Multipixelated Broadband Retarders

Providing a particular broadband or wide-viewing-angle multilayerretarder includes determining the thickness and orientation of themultilayer, starting with the known material properties of the retarderlayer at different wavelengths and angles. The material properties canbe the refractive indices of both fast and slow axes, the absorptioncoefficient, the optical dispersion, and the maximum and minimumallowable thicknesses. The thickness and orientation of the multilayerare calculated to achieve the target retardance of the resultantretarder, e.g., by the following procedure:

(a) A sample is made, including co-aligned PPN and LCP materials appliedto a desired substrate at known thicknesses. The phase retardance,ϕ(λ,θ), of the sample is measured using a commercial polarimeter orellipsometer. The measurement data for ϕ(λ,θ) is fitted with a fittingfunction for subsequent extrapolation and interpolation.

(b) The Jones matrix or Mueller matrix formalism is used to calculatethe theoretical retardance of the multilayer structure as a function ofwavelength, angle, thickness, and orientation by using the measurementdata obtained in (a).

(c) A merit function is defined as:

$\begin{matrix}{{{Least}\mspace{14mu} {square}\mspace{14mu} {deviation}} = {\sum\limits_{{{wavelength}\mspace{14mu} {range}},{{angle}\mspace{14mu} {range}}}^{\;}\left( {{\varphi \left( {\lambda,\theta} \right)} - \varphi_{0}} \right)^{2}}} \\{= {\int_{\lambda_{\min}}^{\lambda_{{ma}\; x}}{\int_{\theta_{\min}}^{\theta_{{ma}\; x}}{d\; \lambda \; d\; {\theta \left( {{\varphi \left( {\lambda,\theta} \right)} - \varphi_{0}} \right)}^{2}}}}}\end{matrix}$

where the wavelength range spans from λ_(min) to λ_(max), and the anglerange spans from θ_(min) to θ_(max). ϕ₀ is the target retardance at aspecific wavelength and a specific angle. An alternative version of themerit function can be defined to speed up the calculation and reducecalculation errors.

(d) The optimal thickness and angle of the multilayer structure iscalculated using an optimization algorithm to minimize the meritfunction defined in (c).

Example 11: Broadband or Wide-Angle Retarder Comprising Two LCP Layers

FIG. 15 illustrates an exemplary broadband or wide-angle retardercomprising two LCP layers (LCP₁ and LCP₂) and one barrier layer B. EachLCP layer has a respective alignment layer (A₁, A₂) with which it isaligned. For simplicity, only three layers are illustrated, althoughmore layers can be added above or below the three layers. In general,the number of LCP layers (each with its respective liquid-crystalorientation) is at least two, but the number actually used is kept to aminimum (at least two) because additional layers can increasemanufacturing defects and costs without providing significantcompensating benefit. The three layers are shown separated from eachother for illustrative purposes, but actually are stacked. The axes x, yand x′, y′ are the fast and slow axes, respectively, of the LCPpolarizer. The z axis is perpendicular to the plane defined by the axesx and y.

In this embodiment the LCP layer 1 (LCP₁) is made of polarizing material1 having thickness t₁. The barrier layer is SiO₂, having a thickness of50 nm, for example. The LCP layer 2 (LCP₂) is made of a polarizingmaterial 2 having thickness t₂. Material 1 can be the same as material2, although it is usually desired that they be compositionally differentand have different optical properties. The axis of material 1 isoriented at an angle α from the axis of material 2. (This axis can bethe fast axis or slow axis of the respective birefringent material.) Thevector r, which makes an angle θ with respect to the z axis, representsan incoming or outgoing ray of light. The operating-wavelength rangespans from λ_(min) to λ_(max), and the operating-angle range spans fromθ_(min) to θ_(max). ϕ₀ is the target retardance atλ₀=(λ_(max)+λ_(min))/2 or θ₀=(θ_(max)+θ_(min))/2. The two LCPs of knownthickness are characterized using a polarimeter (Axometrics Inc.,Huntsville, Ala.) for the respective wavelength and angle range. Theresulting experimental data set, such as the retardance or coefficientsof the Mueller matrix, is utilized as the input of a calculation of amerit function. The merit function is defined to minimize the deviationof the retardance for the wavelength and angle range. The optimizationtoolbox in MATLAB (Mathworks Inc., Natick Mass.) can be used tocalculate the thicknesses t₁ and t₂ and the angle α for the optimalbroadband or wide-view-angle retarder.

Example 12: Broadband Retarder Comprising One LCP Layer

For certain applications, especially where the operating wavelengthrange is relatively narrow (e.g., 500 nm±10 nm), it is possible tocreate a retarder utilizing only a single aligned LCP layer. In such aninstance the LCP can be made as a mixture of two or more LCPs havingdifferent respective refractive indexes. The different polymers must bechemically compatible and soluble with each other and must alignindependently in a fixed direction. Alignment is achieved when thedirection of the aligned LCP is uniform within the retarder area. Bychoosing polymers of different dispersions, it is possible to create,for example, a flat retardance over the operating wavelength range.Here, “dispersion” is defined as the variation of refractive index as afunction of wavelength.

Example 13: Broadband Polarizer Comprising Dyes of Different Colors

A broadband circular or elliptical polarizer can comprise a combinationof a broadband retarder, as discussed in Example 11, and a broadbandlinear polarizer, as discussed in Example 10. The wavelength range ofthe broadband linear polarizer can extend, for example, over any of thefollowing ranges: from 400-700 nm, 700-1200 nm, or 400 nm-1000 nm,depending on the design. A broadband linear polarizer can comprise amixture of dichroic dyes in an aligned LCP. The dichroic dyes areselected based on having good solubility and exhibiting good alignmentin the liquid-crystal matrix. Certain commercially available dyes areoptimized for laser applications and tend to be ionic or highly polar.The dyes tend to be soluble only in polar solvents. A polarizer having ahigh extinction ratio requires a high concentration of dye in thesolvent, and this is often limited by the dye's solubility. Thissolubility depends on both the dyes and the solvents. Candidate solventsinclude, but are not limited to, chloroform, acetone, methanol, THF,PGMEA, toluene, NMP, cyclohexane, and cyclopentanone.

Besides the solvent selected for the dye(s), the solvent for the LCP isselected for its ability to form well-aligned liquid-crystal films. Ingeneral, the equilibrium vapor pressure of the solvent desirably is lowso as to obtain good alignment of the liquid crystal with its respectivealignment layer. The boiling temperature of the solvent desirably islower than the temperature of the liquid-crystal phase-transition point(e.g., ˜75° C. for RMM141C made by EMD Millipore Corp., Philadelphia,Pa.). A mixture of two or more solvents can be effective for dissolvingand aligning dye molecules in the liquid crystal matrix. Among suitablesolvents, PGMEA, toluene, NMP, cyclohexane, and cyclopentanone haverelatively high boiling temperatures (>75° C.), making them less usefulfor aligning the dye and liquid crystal. On the other hand, acetone is agood solvent for DLS-910B and DLS-912C (dyes made by CrystaLyn, Inc.,Binghamton N.Y.) and has a fairly high equilibrium vapor pressure. Basedon experience with the different solvents, a mixture of chloroform andacetone can be used to slow down evaporation to improve the alignment ofthe LCP. By way of example, a 2:1 mixture of chloroform:acetone canprovide good alignment of dye molecules in the liquid crystal matrix. Atroom temperature, the vapor pressure desirably is less than 150 mmHg toobtain good alignments. For example, the vapor pressure of chloroform isabout 110 mmHg Vapor pressures of acetone and toluene are about 200 mmHgand 30 mmHg, respectively. The vapor pressure of a mixture of thesesolvents is approximately 150 mmHg.

Example 14: Broadband Polarizer Comprising a Wire-Grid Linear Polarizer

A broadband circular or elliptical polarizer can be formed by using acombination of a broadband retarder, as discussed in Example 11, and awire-grid linear polarizer. A wire-grid linear polarizer comprises anarray of metallic wire (e.g., Al or Ag). The wire-grid polarizertransmits light having the electric field vector perpendicular to thewire and reflects light with the electric field vector being parallel tothe wire. The polarizer can be placed above or below a broadbandretarder by using interference lithography, imprint lithography, or EUVlithography. The thickness of individual wires typically ranges from 20nm to 250 nm, and the separation between adjacent wires typically rangesfrom 40 nm to 500 nm. A transparent, planarized barrier layer can beused to separate the wire grid polarizer from the broadband retarder. Anantireflection layer can be added with the wire-grid polarizer toincrease transmission of light.

Example 15: Optimized Elliptical Polarizer in a Broadband Polarimeter

Measurements of the four Stokes parameters, representing thepolarization state of light, require at least four measurements usingfour different polarization filters. These measurements can be performedusing a DoFP polarimeter, where each pixel measures a differentelliptical polarization state.

A device according to this example is depicted in FIG. 16. The devicecomprises a glass substrate, a first patterned retarder layer(comprising a first alignment layer A₁ and first LCP layer L₁), a firstisolation (barrier) layer B₁, a second patterned retarder layer(comprising a second alignment layer A₂ and second LCP layer L₂), asecond isolation (barrier) layer B₂, and a uniform polarizer layer(comprising a third alignment layer A₃ and third LCP layer L₃. Thebirefringent material in the first retarder is different from thebirefringent material in the second retarder. For the uniform verticalpolarizer and patterned retarder, a 135° retarder can be used, havingfast-axis angles of ±15.1° and ±51.7°. In this example, each retarder ispixelated. With the retarders being pixelated, this example provides anarray of elliptical polarizers A, B, C, D, each comprising the uniformvertical polarizer and respective regions of the patterned retarders.The device is shown in FIG. 16, having a configuration as described inExamples 13 and 14. This broadband elliptical polarizer array issituated on a glass wafer or other transmissive substrate. The wafer issubsequently diced to form a quantity of individual filters, and thefilters are aligned and mounted on a CCD or CMOS sensor. The dimensionsof the filter desirably match corresponding dimensions of a pixel of thesensor. Alternatively, the broadband elliptical polarizer array can befabricated directly on the sensor wafer, in which case alignment markson the sensor wafer are useful for aligning to the elliptical polarizerlayers.

Example 16: Wide-Angle Liquid-Crystal Display Including BroadbandPolarizer

A liquid-crystal display according to this example comprises a piece ofliquid-crystal display panel and two sets of broadband polarizers. Thepolarizers operate at wide angles as shown in FIG. 17. The broadbandpolarizer operable at wide angles comprises a compensation retarder anda polarizer. The combination of two compensation retarders, 1 and 2, andthe liquid-crystal panel forms a tunable broadband and wide-angleretarder. The configuration is similar to Example 11 but has threeliquid-crystal layers instead of two. The compensation retarder 1comprises material 1 having a thickness denoted t₁. A commercialliquid-crystal panel has specific polarization properties depending onits driving voltage. Example driving voltages range from 3 to 15V. Thecompensation retarder 2 comprises material 2 having a thickness denotedt₂. Material 1 can be the same as material 2, or the materials aredifferent. The axis of material 1 is oriented at an angle α from theaxis of the liquid crystal panel, and the axis of the liquid-crystalpanel is oriented at an angle β from the axis of material 2. Theoperating wavelength range spans from λ_(min) to λ_(max) and theoperating angle range spans from θ_(min) to θ_(max). ϕ₀ is the targetretardance at λ₀=(λ_(max)+λ_(min))/2 and θ₀=(θ_(max)+θ_(min))/2.Materials 1 and 2, and the liquid-crystal panel, are characterized usinga polarimeter (Axometrics Inc., Huntsville, Ala.) for the wavelength andangle range. The experimental data set is utilized as the input of thetheoretical calculation. A merit function is defined to minimize thedeviation of the retardance for the wavelength and angle range. Fortwisted nematic LCD, the angle range is about 160-170 degrees. Formulti-domain vertical alignment (MVA) or in-plane switching (IPS) panel,the standard view angle is about 178 degrees. The optimization toolboxin MATLAB (Mathworks Inc., Natick Mass.) can be used to calculate thethicknesses t₁ and t₂ and the angles α and β for the particularconfiguration of the broadband and wide-angle display.

Example 17: Organic LED Display Comprising Wide-Angle BroadbandPolarizer

A stereoscopic, spatially multiplexed 3-D display requires a patternedpolarization panel. The user can see images of different polarizationsby wearing polarization-selective goggles, for example. An examplepatterned polarization panel comprises an OLED display with a broadbandpolarizer that operates at wide angles. FIG. 18 illustrates a broadbandwide-angle 3-D OLED display comprising an OLED panel and a broadbandpolarizer. The broadband polarizer can be a linear, circular, orelliptical polarizer and can include a broadband wide-angle retarder anda linear polarizer, as discussed in Examples 13 and 14. The broadbandpolarizer can cover the red, green, and blue spectra. Using thisconfiguration, the output polarization of the 3-D display can beoptimized over the wavelength range from λ_(min) to λ_(max) and theoperating angle range from θ_(min) to θ_(max), as discussed in Example11.

The various embodiments described above are not limited to sensingand/or emitting light only in the visible-light portion of theelectromagnetic spectrum. The embodiments are readily applied to otherwavelength ranges in portions such as near, short, mid, and farinfrared.

In view of the many possible embodiments to which the principles of thedisclosed technology may be applied, it should be recognized that theillustrated embodiments are examples and should not be taken as limitingin scope. We therefore claim all that comes within the scope and spiritof the appended claims.

We claim:
 1. An optical device, comprising: a substrate; a color filterarray; and first and second retarder layer groups forming a layer stackon the substrate, the first retarder layer group comprising a firstalignment layer and a first liquid-crystal-polymer (LCP) layer, thefirst LCP layer including molecules aligned with molecules in the firstalignment layer; the second retarder layer group comprising a secondalignment layer and a second LCP layer, the second LCP layer includingmolecules aligned with molecules of the second alignment layer; and apolarization layer group in the stack, the polarization layer groupcomprising a respective alignment layer and a respective LCP layer, therespective LCP layer including molecules aligned with molecules of therespective alignment layer, wherein the optical device is pixelated,wherein each pixel is responsive to different respective polarizationstates of incident light at different colors, wherein the polarizationstates are linear, elliptical, and/or circular polarization states. 2.The optical device of claim 1, further comprising at least a firstbarrier layer situated in the stack between the first and secondretarder layer groups.
 3. The optical device of claim 1, wherein thepolarization layer group and at least one of the first and secondretarder layer groups are pixelated.
 4. The optical device of claim 1,wherein at least one of the first and second retarder layer groups isuniform.
 5. The optical device of claim 1, wherein at least one of thefirst and second retarder layer groups is pixelated.
 6. The opticaldevice of claim 1, further comprising a second barrier layer, wherein:the first barrier layer is disposed in the stack on the first retarderlayer group; and the second barrier layer is disposed in the stack onthe second retarder layer group.
 7. The optical device of claim 1,wherein: the first retarder layer group is patterned; the secondretarder layer group is patterned; and the polarization layer group isuniform.
 8. The optical device of claim 1, wherein the substratecomprises a rigid, inert member that is transparent to a light fluxincident on the stack.
 9. The optical device of claim 1, wherein thepolarization layer group is pixelated, and further comprising a detectorarray, wherein a pixel pitch of the pixelated polarization layer groupis the same as or an integer multiple of a pixel pitch of the detectorarray.
 10. The optical device of claim 1, wherein one of the retarderlayer groups is pixelated, and further comprising a detector array,wherein a pixel pitch of the retarder layer group is the same as or aninteger multiple of a pixel pitch of the detector array.
 11. An opticaldevice, comprising: a substrate; a color filter array; first and secondretarder layer groups forming a layer stack on the substrate, the firstretarder layer group comprising a first alignment layer and a firstliquid-crystal-polymer (LCP) layer, the first LCP layer includingmolecules aligned with molecules in the first alignment layer; thesecond retarder layer group comprising a second alignment layer and asecond LCP layer, the second LCP layer including molecules aligned withmolecules of the second alignment layer; and a linear polarizer in thestack, wherein the optical device is pixelated and configured as anambient light sensor, wherein each pixel is responsive to differentrespective polarization states of incident light in respective colors,wherein the polarization states are linear, elliptical and/or circularpolarization states.
 12. The optical device of claim 11, wherein thelinear polarizer in the stack is pixelated, and further comprising adetector array, wherein a pixel pitch of the linear polarizer in thestack is the same as or an integer multiple of a pixel pitch of thedetector array.
 13. The optical device of claim 12, wherein at least oneof the first and second retarder layer groups is pixelated, and furthercomprising a detector array, wherein a pixel pitch of a pixelatedretarder layer group is the same as or an integer multiple of a pixelpitch of the detector array.
 14. An optical device, comprising: asubstrate; first and second retarder layer groups forming a layer stackon the substrate, the first retarder layer group comprising a firstalignment layer and a first liquid-crystal-polymer (LCP) layer, thefirst LCP layer including molecules aligned with molecules in the firstalignment layer; the second retarder layer group comprising a secondalignment layer and a second LCP layer, the second LCP layer includingmolecules aligned with molecules of the second alignment layer; and apolarization layer group in the stack, the polarization layer groupcomprising a respective alignment layer and a respective LCP layer, therespective LCP layer including molecules aligned with molecules of therespective alignment layer, wherein the device is pixelated andconfigured as a color and polarization mask, wherein each pixel isarranged to generate different respective polarization states of lightat different colors, wherein the polarization states are linear,elliptical, and/or circular polarization states.
 15. The optical deviceof claim 14, further comprising an opaque patterned layer.
 16. Theoptical device of claim 15, wherein the opaque patterned layer issituated on the substrate and the first and second retarder layer groupsform the layer stack on the opaque patterned layer.
 17. The opticaldevice of claim 14, wherein the polarization layer group and at leastone of the first and second retarder layer groups are pixelated.
 18. Theoptical device of claim 14, further comprising a patterned and partiallyopaque layer.
 19. The optical device of claim 14, further comprising atransparent patterned layer.
 20. The optical device of claim 19, whereinthe transparent patterned layer is situated on the substrate and thefirst and second retarder layer groups form the layer stack on thetransparent patterned layer on the substrate.